Airtel — Getting blank calls from a mobile number

Dear Sir,
Myself is Indranil Mukhopadhyay, staying in Chennai with my family for the past one year. My wife is having a hutch connection, and she is continuously getting blank calls from a number [protected]. We suspect it is some Airtel Kolkata number. I tried calling the person from my mobile, but he picks up the phone and after a while just disconnects it. Please help me out with this. It is totally destroying the peace of mind for the entire family, as he is giving calls at odd times as well. Today he called at around 6:00 AM in the morning, and I need this to stop. Would expect a response from you at an earliest.

Thanks and regards,
Indranil Mukhopadhyay
Associate Manager,
CSC India Pvt. Ltd.
Unit 13 & 14,
SDF Buildings,
MEPZ, SEZ Campus,
Chennai - 600 045.